Utilization of waste heat of furnace gases



Feb. 16 1926.

H. H. sTouT UTILIZATION OF WASTE HEAT 0F FURNACE GASES Filedv sept. 17,1920 l l f Patented Feb. 16, 1926.

HARRY HOWARD STOUT, OF DOUGLAS, ABIZONI'A.

UTILIZATION OF WASTE lHEAT OF FURNACE GASES.

Application led September 17, 1920. Serial No. 410,998.

To all whom t may concern:

Be it known that I, HARRY HOWARD STOUT, a citizen of the United States,residing at Douglas, in the county of Cochise 5 and State of Arizona,have invented a new and useful Improvement in Utilization of Waste Heatof Furnace Gases, of which they following is a specification.

This invention relates to waste heat boilers for generation of steam byutilization of the waste heat in gases passing from metallurgicalfurnacesp cement kilns, or other furnaces producin hot gases containingmore or less dust, ume, or suspended material. A serious diiiiculty inthe operation of such waste heat boilers arises from the deposition ofsuch suspended material on the boiler tubes, particularly where thetemperature of the gases is so high that such material deposits in fusedor partly fused condition, forming a hard adherent deposit.

These deposits clog the passages between the boiler tubes and interferewith the assage of the gases and also interfere wlth the transmission ofheat from thegases to the boiler tubes, and it is necessary to removethe deposits from time to time, this requiring opening of the firedoors, or even shutting down the boilers temporarily while the boilertubes are being cleaned, with resultling diminution in steam production.

The main object of this invention is to prevent or reduce theaccumulation of such adherent deposits on the boiler tubes. A furtherobject of the invention is to provide a Waste heat boiler constructionin which the boiler tubes are'out of the direct path of the hot dustygases so that such gases do not encounter obstructing surfaces tendingto receive the fused or semi-fused deposits. Another object of theinvention is to provide for absorbing heat from the hot gases by meanswhich do not obstruct the flow of gases and for radiating the heat soabsorbed to steam boiler tubes which are out of the direct path of thegases.

The accompanying drawings illustrate apparatus suitable for carrying outmy invention, and referring thereto:

Fig. 1 is a diagrammatic plan view, partly in section, of a furnace andwaste heat boiler installation embodying the invention;

Fig. 2 is a vertical section on line 2--2 in Fig. 1;

Fig. 3 is a transverse section .on line 3-3 in Fig. 2.

My invention is a plicable in connection with various kinds ok furnaces,for exam le, reverberatory, or other `metallurgical rnaces, cementkilns, or other furnaces or kilns whose eluent gases contain dust orfume constituent at such high temperature as to tend to collect onobstructing surfaces in a more or less fused condition. In Fig. 1 ofthedrawing I have, by way of example,

illustrated the application of the invention to a reverberatory furnace,indicated atl. An outlet flue 2 is connected to such furnace to receivethe hot gases therefrom, the walls (including the top 3 and floor 4, aswell as the side walls 5 of the tlu'e) being of suitable refractoryconstruction, such as firebrick, so as to be adapted to be heated t0high temperature by contact with the hot furnace gases.

Located alongside of the flue 2 are a series or plurality of steamboiler units 6, each mounted, for example, in a bay, recess or boilerchamber 7, beside the flue, so as to be out of the direct path of thegases pass- .ing inthe flue but exposed to radiation of heat from theopposite side wall as Well as from adjacent roof and floor portions ofthe flue, the water tubes 8 of said boilers being, therefore, heatedlargely by radiation. It will be understood that while the main gasstream passes in a general longitudinal direction through iue 2 Withoutpassing in direct contact with the water tubes 8 in recesses 7, thereare of course some local convection currents or eddy currents in saidrecesses and around said tubes. Some heat is therefore imparted to thewater tubes by convection, in addition to' the heat derived by radiationfrom the hot walls of the flue facing the Water tubes. Said Water tubespreferably extend more or less in the direction of the gas iiow so as tominimize any obstructing elect they may present, but can be vertical, asshown at the right hand side of Fig. 3. Successive boilers, or boilerunits, are preferably arranged alternately on opposite sides of the flueas shown in Fig. 1 so as to permit the exposed radiating portions of theside walls to be distributed with maximum uniformity throughout thelength of the flue and on both sides thereof and therefore enable suchveo radiating side walls t-o more uniformly and effectively take up theheat from the gases passing in the Hue.

In case any material collects on the boiler tubes it may be removed fromtime to time, the boiler chamber being shut oHl from Hue 2 at such timeby means of a partition or curtain Wall 10, which is normally supportedby suitable means 11 and is brought into position between the Hue andthe boiler chamber, when required, the boiler tubes being then cleanedin the usual manner.

The gases may pass from Hue 2 through conduits 12 to additional heatutilizing means comprising steam boilers 13, mounted in boilerchambersor settings 14 in the usual .manner of Waste heat boilers, thegases Hnally passing by Hues 15 to suitable stack means.

The operation of the invention is as follows:

The hot gases coming from furnace 1 pass through the Hue 2 and give up apart of their heat to the Hue Walls, which are thereby heated to a hightemperature and caused to radiate heat to the boiler tubes opposite oradjacent thereto. The boiler tubes also receive some-heat directly fromthe gases,

but as the gas 'stream does not impingedi-- rectly on the boiler tubesthere is little tendency for deposition of suspended material on thetubes. The Hue presents suHicient heat absorbing and radiating surfaces,including top 3, Hoor 4, and the unrecessed portions of the side Walls5, to reduce the temperature of the gases inpassing through the Hue toor below the fusing pointof any constituent liable to be deposited onthe boiler tubes, and as the gases pass from the Hue they are thereforeat such temperature that any suspended material theyimay contain is insolid conditions or sufficiently cooled to prevent the formation of afused or semi-fused deposit. The eHiuent gases from the Hue 2 maytherefore be passed `l'hrough the Water'tube, or other boilers 13,Without liability of forming an adherent deposit thereon, and any solidmaterial that may collect on the tubes of such boilers may be readilyremoved.

In the application of the invention to gases from reverberatory furnacesused in copper smelters, the gases, as they leave the furnace, have atemperature of about 2300o F., at which temperature the suspended ma-ILerial in the gases tends to form a more or less molten deposit, and inpassing through the Hue the gases should be reduced in temperature toabout 1-100o F., at Which temperature the suspended material is solid.

My invention is applicable with advantage to other kinds of furnaces,for example, to cement kilns using Waste heat boilers and producingeHiuent gases containing fusible constituents; for example, alkali-metalcompounds which tend to fuse onto the boiler tubes. This is especiallythe case Where an agent,vsuch as sodium chloride, is used to increasethe volatilization of potassium compound from the raw mix in the kiln,and has heretofore been considered as preventing the use of such anagent where Waste heat utilization is required. By operation of theprocess above described, the gases from the kiln may irstbe reduced intemperature in a preliminary radiation boiler plant, for example, of theconstruction described, and the gases then passed through an ordinaryWaste heat boiler installation to further utilize the heat thereof.

While I have shown the boiler units as arranged at the sides of the Huethrough which the hot gases pass, and in alternate arrangement, it Willbe understood that they may be arranged in any position adjacent to thegas stream but out of the direct path of the gas, and may be of anydesired number and closeness of arrangement, according to therequirement of any particular case.

By reason of the suspended matter contained in the gasses passingthrough the Hue and adjacent to or alongside the boiler tubesconsiderable radiation may take place from such suspended matterdirectly to the boiler tubes, and in some cases, this may be animportant factor in the operation of the boilers.

As shown in Figs. 1 and 2, means, such as a lWater pipe 20, may beprovided at the bridge Wall below the outlet of the furnace 1, so thatthe molten slag will not break through into the boiler setting.

What I claim is: l

1. In combination with a furnace, a Hue adapted to receive hot gassestherefrom, and having a heat-absorbing and heat-radiating side Wall, andhaving a lateral recess opposite said Wall and in open communicationwith the Hue passage, steam boiler means in said recess, out of thedirect path of such gases through the Hue, and adapted to receive heatby radiation from said side Wall, and partition means movably mountedadjacent to the flue and adapted to be moved into position between saidrecess and said Hue, to temporarily shut off said boiler means from theHue.

2. Means for utilizing heat of furnace gases comprising a Hue forpassage of the gases and having heat absorbing and heatradiating Walls,and a plurality of steam boiler units arranged along the Hue in opencommunication therewith and out of the direct path of the gases throughthe Hue, and in alternate arrangement on opposite sides of the Hue, sothat the boiler units alternate with radiating Wall portions and aradiating Wall portion is opposite each boiler unit.

3. Means for utilizing heat of furnace gases comprising a Hue adaptedfor passage i of the gases and having heat-absorbing and heat-radiatingwalls,

and a plurality of 5 rect 'path of the each boiler unit jacent Wallportions of th heat by radiation from opg gases passing inthe Hue, beingadapted to receive osite and adue, and partition means ada ted to bebrought into position between the Hue and the respective boiler units toshut off any boiler unit from the Hue independently of the othenunits.

In testimony whereof I have hereunto subscribed my name this 31st day ofAugust, 1920.

HARRY HOWARD STOUT.

